REQUISITE VARIETY 11/11 



by the invention of some new device or some new electronic circuit, 

 or the discovery of some new element. It does not even have any- 

 thing to do with the properties of the machine in the general sense 

 of Chapter 4; for it comes from the Table, such as that of S. 11/4; this 

 Table says simply that certain D-R combinations lead to certain 

 outcomes, but is quite independent of whatever it is that determines 

 the outcome. Experiments can only provide such tables. 



The theorem is primarily a statement about possible arrangements 

 in a rectangular table. It says that certain types of arrangement 

 cannot be made. It is thus no more dependent on special properties 

 of machines than is, say, the "theorem" that four objects can be 

 arranged to form a square while three can not. The law therefore 

 owes nothing to experiment. 



11/11. Regulation again. We can now take up again the subject 

 of regulation, ignored since the beginning of this chapter, for the 

 law of Requisite Variety enables us to apply a measure to regulation. 

 Let us go back and reconsider what is meant, essentially, by 

 "regulation". 



There is first a set of disturbances D, that start in the world outside 

 the organism, often far from it, and that threaten, if the regulator 

 R does nothing, to drive the essential variables E outside their 

 proper range of values. The values of E correspond to the "out- 

 comes" of the previous sections. Of all these £'-values only a few 

 {rj) are compatible with the organism's life, or are unobjectionable, 

 so that the regulator R, to be successful, must take its value in a 

 way so related to that of D that the outcome is, if possible, always 

 within the acceptable set t], i.e. within physiological limits. Regula- 

 tion is thus related fundamentally to the game of S.11/4. Let us 

 trace the relation in more detail. 



The Table T is first assumed to be given. It is the hard external 

 world, or those internal matters that the would-be regulator has to 

 take for granted. Now starts a process. D takes an arbitrary value, 

 R takes some value determined by Z)'s value, the Table determines 

 an outcome, and this either is or is not in tj. Usually the process 

 is repeated, as when a water-bath deals, during the day, with various 

 disturbances. Then another value is taken by D, another by R, 

 another outcome occurs, and this also may be either in t] or not. 

 And so on. If i? is a well-made regulator — one that works success- 

 fully — then R is such a transformation of D that all the outcomes 

 fall within 17. In this case R and T together are acting as the barrier 

 F(S.10/5.) 



14 209 



